a) Field of the Invention
The present invention relates to apparatus and method for automatically controlling a vehicular velocity for a vehicle so as to follow up a preceding vehicle which is running ahead of the vehicle, maintaining appropriately an inter-vehicle distance to the preceding vehicle.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 3-153426 published on Jul. 1, 1991 exemplifies a previously proposed automatic vehicular velocity controlling system to maintain a set cruise speed of the vehicle (also, called an auto cruise speed control system).
In the disclosed auto cruise speed control system, an automatic cruise control function is provided to control the vehicular velocity so as to maintain the set vehicular velocity. If a wheel slip occurs on the vehicle in which the auto cruise control system is mounted, a traction control function is provided which reduces an engine output (torque or power) with an engine throttle valve closed according to a slip rate of the wheel slip. In this control, a traction control is outputted from a traction control system to the auto cruise control system. This auto cruise control system determines whether the traction control signal is inputted thereto during a normal auto cruise control operation. If the traction control signal is not inputted, the auto cruise control is continued. If the traction control signal is inputted, the auto-cruise control is inhibited with a higher priority placed on the traction control.
In the above-described previously proposed automatic cruise control system, the auto cruise control is inhibited with the traction control signal inputted to place a higher priority on the traction control so as to prevent both controls from being interfered against each other. However, since the control priority is placed on the traction control, the traction control is executed with the auto cruise speed control released when a road surface condition is transferred from a high frictional coefficient road surface such as a dry paved road to a low frictional coefficient road surface such as a snowy, a frozen, and a wet road.
In a case where if the above-described priority control is applied to a follow-up run control which is an evolution type of the auto cruise control and which maintains the inter-vehicle distance to a preceding vehicle which is running ahead of the vehicle constant, the preceding vehicle follow-up run control is released while the traction control is executed. To secure the inter-vehicle distance, the brake operation is needed with a vehicular driver.
Hence, it is, therefore, an object of the present invention to provide vehicular automatic vehicular velocity controlling apparatus and method in which an inter-vehicle distance is maintained by retarding a timing of a release of the follow-up run control under a brake control when the vehicle in which the automatic vehicular velocity controlling apparatus is mounted is running on a low frictional coefficient road surface.
According to one aspect of the present invention, there is provided with an apparatus for automatically controlling a vehicular velocity for a vehicle, comprising: an inter-vehicle distance detector to detect an inter-vehicle distance of the vehicle to a preceding vehicle which is running ahead of the vehicle; a target vehicular velocity variation rate calculating section that calculates a target vehicular velocity variation rate to make the detected inter-vehicle distance substantially equal to a target inter-vehicle distance; a vehicular run controlling section that is enabled to perform a vehicular run control to maintain the target vehicular velocity variation rate; a release condition detector to detect whether a release condition of the vehicular run control by the vehicular velocity controlling section is established; and a vehicular run control releasing section that releases the vehicular run control at a time at which a vehicular deceleration control is completed, when the vehicular run controlling section is detected to be performing the vehicular deceleration control and the release condition detector detects that the release condition is established.
According to another aspect of the present invention, there is provided with a method for automatically controlling a vehicular velocity for a vehicle, comprising: detecting an inter-vehicle distance of the vehicle to a preceding vehicle which is running ahead of the vehicle; calculating a target vehicular velocity variation rate to make the detected inter-vehicle distance substantially equal to a target inter-vehicle distance; performing a vehicular run control to maintain the target vehicular velocity variation rate; detecting whether a release condition of the vehicular run control is established; and releasing the vehicular run control at a time at which a vehicular deceleration control to perform the vehicular run control to maintain the target vehicular velocity variation rate is completed, when the vehicular deceleration control is performed and the release condition is established.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.